function w = integrate (w,method)
   %INTEGRATE integrates a waveform signal
   %   waveform = integrate(waveform, [method])
   %   goes from Acceleration -> Velocity, and from Velocity -> displacement
   %
   %   wave = integrate(waveform)  or
   %   wave = integrate(waveform,'cumsum') performs integration by summing the
   %   data points with the cumsum function, taking into account time interval
   %   and updating the units as appropriate.
   %
   %   waveform = integrate(waveform, 'trapz') as above, but uses matlab's
   %   cumtrapz function to perform the integration.
   
   %   Input Arguments
   %       WAVEFORM: a waveform object   N-DIMENSIONAL
   %       METHOD: either 'cumtrapz' or 'cumsum'  [default is cumsum]
   %
   %   Actual implementation  merely does a cumulative sum of the waveform's
   %   samples, and updates the units accordingly.  These units may be a
   %   little kludgey.
   %
   %
   %   See also CUMSUM, CUMTRAPZ, WAVEFORM/DIFF
   
   % AUTHOR: Celso Reyes, Geophysical Institute, Univ. of Alaska Fairbanks
   % $Date$
   % $Revision $
   
   Nmax = numel(w);
   allfreq = get(w,'freq');
   
   if ~exist('method','var')
      method = 'cumsum';
   end
   
   switch lower(method)
      case 'cumsum'
         integratefn = str2func('cumsum');
      case 'trapz'
         integratefn = str2func('cumtrapz');
      otherwise
         error('Waveform:integrate:unknownMethod',...
            'Unknown integration method.  Valid methods are ''cumsum'' and ''trap''');
   end
   
   for I = 1 : Nmax
      w(I) = set(w(I),'data',integratefn(w(I).data) ./ allfreq(I));
      tempUnits = get(w(I),'units');
      whereInUnits = strfind(tempUnits,' / sec');
      if isempty(whereInUnits)
         w(I) = set(w(I),'units', [tempUnits, ' * sec']);
      else
         tempUnits(whereInUnits(1) :whereInUnits(1)+5) = [];
         w(I) = set(w(I),'units',tempUnits);
      end
      %w(I) = set(w(I),'units', [get(w(I),'units'), ' * sec']);
   end
end